One US soldier was killed and another wounded in an "apparent insider attack" in Kabul on Saturday, NATO said, in the latest such assault on international forces in Afghanistan. "Initial reports indicate the attacker was a member of the Afghan National Defense and Security Forces," NATO`s Resolute Support mission said in a statement. The attacker was killed by "other Afghan forces", it added. The wounded soldier was flown to Bagram Airfield north of the Afghan capital where he was receiving medical treatment. He was in a "stable condition". An investigation into the incident was underway, the statement said.